1. Field of the Invention
The present invention relates to a light measuring device having an automatic focus control mechanism including one-shot type focus control means for effecting focus control in one-shot type focus control mode and servo type focus control means for effecting focus control in servo type focus control mode, in which a field to be photographed is divided into a plurality of areas which are subjected to light-measurement.
2. Description of the Related Art
Recently, a plurality of types of camera provided with an automatic focussing mechanism (hereinafter, referred to as AF) have become widely used. The AF control mode now employed in the camera of this kind can be classified into servo type focus control mode (hereinafter referred to as "servo mode") and one-shot type focus control mode (hereinafter referred to as "one-shot mode"). According to the servo mode, a photographing lens is always focussed onto an object to be photographed by the action of the AF so long as a power is supplied to the AF (for example, in the state where a releasing button is held pushed to its first stroke) and if the object has moved the photographing lens is automatically operated so that the photographing lens becomes focussed again onto the object moved. Accordingly, the servo mode is suitable to take a photograph of a moving object which moves within a distance measuring range of the camera.
On the other hand, according to the one-shot mode, a photographing lens is operated by the AF so that it is focussed onto an object to be photographed when a power is supplied to the AF, but even if the object moves after the lens has been once focussed onto the object by the AF, the photographing lens is not operated. In order to attain the focussing, it is required to release and reset the power. That is, the lens is focussed onto the object only one time after starting the operation of the AF. Accordingly, the one-shot mode is suitable to take a still photograph of person, scenery, souvenier picture, close-up picture or the like.
There are various types of light measuring system now employed in a camera, which include a center-weighted measuring type, an average measuring type, a partial measuring type, a spot measuring type, a divided measuring type, an estimated measuring type and the like. Any one of these various types of the light measuring system can be selected by a photographer as he desires. The existence of such various types of the AF mode and various types of the light measuring system, which can be selectively used by the photographer, is considerably advantageous to a skilled photographer but it is rather inconvenient to a beginner since the operation of the camera is complicated and troublesome so that he may make erroneous operation.
The estimated measuring method as mentioned above is a light measuring system which includes dividing a field to be photographed into a plurality of areas, effecting light-measurement of the respective areas and selecting particular arithmetic equatron from a plurality of arithmetic equations for light-measurement on the basis of luminance difference informations or the like at the respective divided areas to find a proper light measurement value.
When this estimated light measuring method is employed, there arises such disadvantage that a value of light measurement found by the predetermined process may not fully match with the AF mode as selected.